Schematic
This section contains the detailed electronic schematic of the Archean synthesizer. The schematic diagram is an essential resource for understanding how the circuit components are connected and how the overall system operates
.
The schematic is available as a downloadable PDF file for convenient viewing and study. It visually represents the entire circuitry including:
• Power supply and voltage regulation
• Oscillators responsible for sound generation
• Filters shaping the sound spectrum
• Envelope generators controlling amplitude and modulation
• Control interfaces such as knobs, sensors, and buttons
• MIDI input/output and communication circuitry
Reading the schematic may seem complex at first, but it follows standard electronic symbols and conventions. By following the signal flow and component connections, you can gain insight into the design and functionality of the synthesizer.
We encourage users to reference the schematic if they want to repair, modify, or customize the hardware. Understanding the schematic alongside the source code will provide a comprehensive view of the Archean synthesizer’s architecture.
Please follow common safety precautions when working with electronic circuits. If you are new to electronics, consider studying basic schematic reading skills and circuit theory to make the most out of this resource.
This section contains the detailed electronic schematic of the Archean synthesizer. The schematic diagram is an essential resource for understanding how the circuit components are connected and how the overall system operates
.
The schematic is available as a downloadable PDF file for convenient viewing and study. It visually represents the entire circuitry including:
• Power supply and voltage regulation
• Oscillators responsible for sound generation
• Filters shaping the sound spectrum
• Envelope generators controlling amplitude and modulation
• Control interfaces such as knobs, sensors, and buttons
• MIDI input/output and communication circuitry
Reading the schematic may seem complex at first, but it follows standard electronic symbols and conventions. By following the signal flow and component connections, you can gain insight into the design and functionality of the synthesizer.
We encourage users to reference the schematic if they want to repair, modify, or customize the hardware. Understanding the schematic alongside the source code will provide a comprehensive view of the Archean synthesizer’s architecture.
Please follow common safety precautions when working with electronic circuits. If you are new to electronics, consider studying basic schematic reading skills and circuit theory to make the most out of this resource.
Teensy 4.0
What is Teensy?
Teensy 4.0 is a small, powerful microcontroller development board created by PJRC (Paul Stoffregen).
Think of it as: A tiny computer optimized for real-time electronics projects.
Technical Specifications
Processor
CPU: ARM Cortex-M7 (NXP iMXRT1062)
Speed: 600 MHz
Architecture: 32-bit ARM
One of the fastest microcontrollers available!
Memory
Flash (Program Storage): 2 MB
RAM: 1024 KB (1 MB)
Why Teensy 4.0 for Archean?
1. Processing Power
600 MHz = Fast enough for:
- 44 kHz audio generation
- Real-time DSP processing
- Multiple simultaneous tasks
- DMA operations
- Complex calculations
2. Audio Performance
Hardware features perfect for synthesis:
Precise Timers:
- IntervalTimer for accurate sample rate
- FlexPWM for modulation
- Microsecond precision
Fast ADC:
- 12-bit resolution
- Multiple channels
- DMA support
- High-speed sampling
Multiple SPI buses:
- Three DACs simultaneously
- Fast communication (20 MHz+)
3. Multiple Communication Buses
Archean uses:
SPI (3 buses available):
- DAC 1: Oscillator audio
- DAC 2: ADSR & Distance
- DAC 3: LFO & Element
I2C (3 buses available):
- Wire1: Touch sensors (MPR121 × 2)
- Wire1: Distance sensor (VL53L0X)
Serial MIDI:
- Hardware UART for traditional MIDI
USB:
- USB MIDI (computer connection)
- Programming interface
4. Arduino Compatibility
Teensy uses Arduino IDE:
- Familiar programming environment
- Huge library ecosystem
- Easy to learn
- Extensive community support
- Cross-platform (Windows, Mac, Linux)
5. Small Form Factor
Tiny size: Teensy 4.0: 36mm × 18mm
Perfect for:
- Portable instruments
- Eurorack modules
- Desktop synthesizers
- Embedded audio devices
Teensy 4.0 makes Archean possible:
✓ Fast enough - 44 kHz audio + real-time control
✓ Enough I/O - Multiple DACs, sensors, MIDI
✓ Real-time - Deterministic timing, no OS
✓ Professional - USB MIDI, low latency
✓ Compact - Tiny footprint
✓ Affordable - $20 for pro features
✓ Easy - Arduino IDE familiarity
✓ Powerful - DMA, multiple buses, fast ADC
Teensy 4.0 is a small, powerful microcontroller development board created by PJRC (Paul Stoffregen).
Think of it as: A tiny computer optimized for real-time electronics projects.
Technical Specifications
Processor
CPU: ARM Cortex-M7 (NXP iMXRT1062)
Speed: 600 MHz
Architecture: 32-bit ARM
One of the fastest microcontrollers available!
Memory
Flash (Program Storage): 2 MB
RAM: 1024 KB (1 MB)
Why Teensy 4.0 for Archean?
1. Processing Power
600 MHz = Fast enough for:
- 44 kHz audio generation
- Real-time DSP processing
- Multiple simultaneous tasks
- DMA operations
- Complex calculations
2. Audio Performance
Hardware features perfect for synthesis:
Precise Timers:
- IntervalTimer for accurate sample rate
- FlexPWM for modulation
- Microsecond precision
Fast ADC:
- 12-bit resolution
- Multiple channels
- DMA support
- High-speed sampling
Multiple SPI buses:
- Three DACs simultaneously
- Fast communication (20 MHz+)
3. Multiple Communication Buses
Archean uses:
SPI (3 buses available):
- DAC 1: Oscillator audio
- DAC 2: ADSR & Distance
- DAC 3: LFO & Element
I2C (3 buses available):
- Wire1: Touch sensors (MPR121 × 2)
- Wire1: Distance sensor (VL53L0X)
Serial MIDI:
- Hardware UART for traditional MIDI
USB:
- USB MIDI (computer connection)
- Programming interface
4. Arduino Compatibility
Teensy uses Arduino IDE:
- Familiar programming environment
- Huge library ecosystem
- Easy to learn
- Extensive community support
- Cross-platform (Windows, Mac, Linux)
5. Small Form Factor
Tiny size: Teensy 4.0: 36mm × 18mm
Perfect for:
- Portable instruments
- Eurorack modules
- Desktop synthesizers
- Embedded audio devices
Teensy 4.0 makes Archean possible:
✓ Fast enough - 44 kHz audio + real-time control
✓ Enough I/O - Multiple DACs, sensors, MIDI
✓ Real-time - Deterministic timing, no OS
✓ Professional - USB MIDI, low latency
✓ Compact - Tiny footprint
✓ Affordable - $20 for pro features
✓ Easy - Arduino IDE familiarity
✓ Powerful - DMA, multiple buses, fast ADC
MIDI In
MIDI Input Schematic
This circuit converts standard 5-pin MIDI signals to 3.3V logic levels for the Teensy 4.0.
Components
R1 - Current Limiting Resistor (220Ω)
Purpose: Limits current through optocoupler LED
D2 - Protection Diode (1N4148)
Purpose: Protects against reverse polarity
Type: Fast switching diode
Function:
- Blocks negative voltage spikes
- Protects optocoupler LED
- No effect on normal operation (reverse biased)
Why needed: MIDI cables can pick up electrical noise
IC3 - Optocoupler (6N138)
What is an Optocoupler?
Two completely separate circuits connected only by light.
Why Use Optocoupler?
1. Electrical Isolation:
- Prevents ground loops
- Protects from voltage spikes
- Stops noise injection
2. Voltage Level Conversion:
- MIDI: 5V current loop
- Teensy: 3.3V logic
- Optocoupler bridges the gap
3. Safety:
- Protects expensive Teensy
- Isolates from faulty MIDI devices
- Standard MIDI specification requirement
R2 - Pull-up Resistor (220Ω)
Purpose: Pulls output HIGH when LED is off
Why needed: Phototransistor only pulls LOW, resistor provides HIGH
How It Works
1. MIDI device sends data:
Transmitter sends: Note On (byte 0x90)
Current flows through MIDI cable
Arrives at Pin 4 and Pin 5
2. Current through LED:
Pin 5 (+5V) → R1 (220Ω) → LED (IC3 pin 2)
LED lights up when current flows
3. Light activates transistor:
LED emits light inside IC3
Phototransistor detects light
Transistor conducts (pulls output LOW)
4. Teensy receives signal:
Output pin 6 goes LOW
Teensy RX pin reads LOW
UART decodes MIDI byte
5. No signal:
No current → LED off
No light → Transistor off
Pull-up resistor → Output HIGH
Teensy reads HIGH (idle state)
Result: Safe, professional MIDI input that works with any MIDI device ever made!
This circuit converts standard 5-pin MIDI signals to 3.3V logic levels for the Teensy 4.0.
Components
R1 - Current Limiting Resistor (220Ω)
Purpose: Limits current through optocoupler LED
D2 - Protection Diode (1N4148)
Purpose: Protects against reverse polarity
Type: Fast switching diode
Function:
- Blocks negative voltage spikes
- Protects optocoupler LED
- No effect on normal operation (reverse biased)
Why needed: MIDI cables can pick up electrical noise
IC3 - Optocoupler (6N138)
What is an Optocoupler?
Two completely separate circuits connected only by light.
Why Use Optocoupler?
1. Electrical Isolation:
- Prevents ground loops
- Protects from voltage spikes
- Stops noise injection
2. Voltage Level Conversion:
- MIDI: 5V current loop
- Teensy: 3.3V logic
- Optocoupler bridges the gap
3. Safety:
- Protects expensive Teensy
- Isolates from faulty MIDI devices
- Standard MIDI specification requirement
R2 - Pull-up Resistor (220Ω)
Purpose: Pulls output HIGH when LED is off
Why needed: Phototransistor only pulls LOW, resistor provides HIGH
How It Works
1. MIDI device sends data:
Transmitter sends: Note On (byte 0x90)
Current flows through MIDI cable
Arrives at Pin 4 and Pin 5
2. Current through LED:
Pin 5 (+5V) → R1 (220Ω) → LED (IC3 pin 2)
LED lights up when current flows
3. Light activates transistor:
LED emits light inside IC3
Phototransistor detects light
Transistor conducts (pulls output LOW)
4. Teensy receives signal:
Output pin 6 goes LOW
Teensy RX pin reads LOW
UART decodes MIDI byte
5. No signal:
No current → LED off
No light → Transistor off
Pull-up resistor → Output HIGH
Teensy reads HIGH (idle state)
Result: Safe, professional MIDI input that works with any MIDI device ever made!
Power in
How does it works
V ref
What is V ref
ADC input
Pitch CV Input Circuit
This circuit conditions external control voltage (CV) for pitch control and converts it to a safe level for the Teensy ADC.
Purpose: Accept 0-10V CV input and scale it to 0-3.3V for the Teensy's analog input.
Components
J4 - CV Input Jack
3-pin jack (TRS or mono):
- Pin 1: Signal (CV input)
- Pin 2: Not connected
- Pin 3: Ground
Expected input: 0V to +10V CV (modular synth standard)
Common sources:
- Sequencers (0-5V or 0-10V)
- Keyboards (1V/octave)
- LFOs
- Envelope generators
- Other modulation sources
Stage 1: Input Buffer (IC5D)
MCP6004 Op-Amp (Channel D)
Configuration: Voltage follower (unity gain buffer)
Connections:
- Pin 12 (-): Connected to output (pin 14)
- Pin 13 (+): Input signal via R6 (100kΩ)
- Pin 14 (Output): Buffered signal
This circuit conditions external control voltage (CV) for pitch control and converts it to a safe level for the Teensy ADC.
Purpose: Accept 0-10V CV input and scale it to 0-3.3V for the Teensy's analog input.
Components
J4 - CV Input Jack
3-pin jack (TRS or mono):
- Pin 1: Signal (CV input)
- Pin 2: Not connected
- Pin 3: Ground
Expected input: 0V to +10V CV (modular synth standard)
Common sources:
- Sequencers (0-5V or 0-10V)
- Keyboards (1V/octave)
- LFOs
- Envelope generators
- Other modulation sources
Stage 1: Input Buffer (IC5D)
MCP6004 Op-Amp (Channel D)
Configuration: Voltage follower (unity gain buffer)
Connections:
- Pin 12 (-): Connected to output (pin 14)
- Pin 13 (+): Input signal via R6 (100kΩ)
- Pin 14 (Output): Buffered signal
DAC for OSC
DAC For functions
Filter
VCA
Distortion
Reverb
Keyboard sensors
White noise